This invention refers to the waterproofing of hydraulic structures such as roller compacted concrete dams (RCC dams), concrete gravity dams and masonry gravity dams, embankment dams with a concrete waterproofing upstream facing, canals, tunnels, reservoirs and similar, and of concrete and masonry structures in general. In particular, this invention concerns a method for the waterproofing of contraction and/or construction joints, deteriorated joints and/or cracks, here in after referred to also as xe2x80x9cjointsxe2x80x9d or xe2x80x9ccracksxe2x80x9d in the concrete or masonry lining or body of hydraulic structures as well as in the concrete and/or masonry structures of the type previously referred to, having a surface in contact with water or a surface with joints and/or cracks through which water seepage can occur; the invention also relates to a layered waterproofing covering device for joints, cracks and the like, obtained by the waterproofing method mentioned above.
According to well known concepts, in the construction of hydraulic structures, for example of concrete dams or roller compacted concrete dams, or in the construction of embankment dams, both earthfill and rockfill, it is necessary to provide a proper waterproofing of the upstream face in order to prevent water seepage from the reservoir, which represents an economic loss and which can compromise the integrity and the stability of the dam body itself.
The constructive methodology of dams and hydraulic structures, or of concrete or masonry structures of any type, has therefore to take into account the shrinkage and thermal expansion phenomena, and the movements due to settlement or to other causes which the hydraulic structure or the concrete structure can undergo over time, for example at variation in hydraulic load on the upstream side of a dam, which can cause the opening or widening of the joints of the concrete waterproofing liner, or the formation of dangerous cracks through which seepage of water could occur.
In particular, in the design and construction of RCC dams it is necessary to consider the deformations induced by the hydration process of the concrete because, after reaching the maximum hydration heat, the decrease of the temperature of the dam body until it reaches a stable condition, is accompanied by contraction phenomena of the concrete volume, which can cause cracking.
Therefore, in these hydraulic structures it is necessary to provide proper contraction joints in order to avoid that uncontrolled cracking can occur.
The contraction joints generally create preferential lines for the formation of cracks in the upstream face of the dam, due to the contraction of the concrete, which develop vertically parallel to the slope.
The contraction joints also undergo some movements, generally to a lesser extent, even after the concrete has reached its equilibrium temperature. These movements can be caused by the variations of the water level in the reservoir, by seismic phenomena, or by other causes.
In general, joints and/or cracks represent a discontinuity in the concrete or masonry waterproofing liner of the upstream face of a dam or of any hydraulic structure or other structure. Therefore this discontinuity must be treated so as to avoid possible water seepage.
The traditional systems which are at present adopted for the waterproofing of joints and/or cracks usually foresee the use of synthetic or copper material, the so-called xe2x80x9cwaterstopsxe2x80x9d, arranged in single or double rows, embedded in the concrete as it is being cast during the construction of the hydraulic structure or other structure, and therefore they interfere with the constructive process.
In general, the employment of the known waterproofing systems, besides interfering with the constructive process, makes it quite difficult to intervene for any maintenance or repair operation, when joints deteriorate. As a matter of fact, these systems generally do not provide a proper waterproofing, durable over time and capable of compensating movements or settlements that should occur in the body of the hydraulic structure or of the concrete and/or masonry structure, without losing their fundamental waterproofing characteristics.
While the contraction joints in RCC dams or the construction joints in concrete dams or similar hydraulic works represent a discontinuity induced in the concrete waterproofing liner, and therefore waterproofed since the construction of the hydraulic work itself, other casual discontinuities can occur during operation, when, for any reason, the concrete or the masonry crack, or the waterstops waterproofing the joints deteriorate over time or for accidental causes.
Therefore, this cracks or deterioration, if not properly protected and checked, can cause water seepage, with damaging consequences.
The general object of this invention is to provide a method for the waterproofing of joints and/or deteriorated joints and/or of cracks in the concrete liners of hydraulic structures such as dams or similar, and in concrete and/or masonry structures, which can remedy the inconveniences of waterproofing systems previously in use.
More in particular, an object of this invention is to provide a waterproofing method as referred to above, which is quite independent from the constructive process of the hydraulic structure or structure and which can be applied subsequently.
Another object of the invention is to provide a method for the waterproofing of joints and/or cracks as mentioned above, which has such a high degree of elastic deformability and of independence of its components, that it can follow any movement which should occur in joints or cracks, subsequent to the movements of the dam body or the hydraulic structure to be protected and/or repaired, without losing the waterproofing and mechanical resistance characteristics.
A further object of the invention is to provide a waterproofing of joints, cracks and the like as previously defined, which is external to the hydraulic structure or other type of structure and which therefore allows control and repair interventions after its installation.
The invention is also aiming to employ a membrane in elastically yieldable synthetic material, for the waterproofing of contraction joints, construction joints, cracks and the like, in particular in the upstream faces or in existing surfaces which get in touch with water in hydraulic structures such as RCC dams, concrete dams, embankment dams having a concrete upstream face, tunnels, water conveyance structures, reservoirs and similar hydraulic structures.
What has been previously mentioned can be provided by means of a method for the waterproofing of joints and/or cracks in the concrete and/or masonry linings or body of hydraulic structures, masonry structures and similar, as well as with a waterproofing covering device for joints, cracks and the like.
In particular, according to the invention, a method has been provided for the waterproofing covering of joints and/or cracks in hydraulic structures, masonry structures and similar, by means of a waterproofing membrane comprising a strip of elastically yieldable synthetic material, which is positioned along a joint or crack on an existing surface of the hydraulic and/or masonry structure to be protected, comprising the steps of:
positioning at least one support element of rigid material on the existing surface of the hydraulic and/or of the masonry structure, to cover the joint and/or crack, and to provide a support surface for the membrane, anchoring said support element across the joint and/or the crack to allow a sliding movement in respect to said existing surface;
positioning at least one protection substrate for the membrane, over the support element, between the latter and the membrane to allow a sliding movement of the same membrane in respect to the support element and the existing surface;
placing the waterproofing membrane over the protection substrate and the support element; and
watertightly fastening the peripheral edges of the membrane to the existing surface of the hydraulic and/or of the masonry structure, along the sides of the joint and/or the crack.
According to another aspect of this invention, over the waterproofing strip of the membrane it is possible to install a protection slab, preferably in steel or another proper material, to cover the waterproofing strip along its whole development or along only a portion of it, anchoring this protection slab in such a way as to allow it independently move in respect to the waterproofing membrane. Should the membrane be employed to waterproof a crack through which water can seep from the back side, the protection slab can be used for frontally supporting the same membrane and avoid its swelling.
According to another aspect of this invention, it is preferable to extend the waterproofing of the joint to waterproofing a concrete beam at the dam heel, extending and positioning the waterproofing covering membrane on a foundation beam, watertightly anchoring the membrane in correspondence of the area where the joints of the foundation beam, if any, are waterproofed.
According to another aspect of the invention a waterproofing covering device for joints and/or cracks on an existing surface of hydraulic or masonry structures has been provided, said covering device comprising:
at least a support element longitudinally extending for at least a portion of the joint or crack, said support element being fastened to the existing surface, so that it can slide in respect to said surface;
a waterproofing membrane comprising a strip of elastically yieldable material, longitudinally extending over the support element and tightly fastened to the existing surface on both sides of the joint or crack;
an intermediate protection substrate between the waterproofing membrane and the support element; and
fastening means for water tightly fastening the waterproofing membrane to the existing surface on both side of the elastically yieldable strip.